Psychologists have produced theories and a wealth of empirical evidence concerning the basic building blocks of social cognition. This understanding has recently benefited from the use of functional magnetic resonance imaging (fMRl) to identify a network of brain regions that support various facets of social cognition in humans. Studies of how we think about ourselves and other minds, how we mimic and respond, and how we regulate our emotions have allowed us to learn about the paths toward better and worse mental health outcomes. However, much of this work has focused on the mature minds of adult humans almost exclusively. lt is becoming clear that in order to understand the basis of mental health and illness in adults, it is important to understand the development of social cognition in children because such a focus can provide the crucially needed early view of intricate mental processes during formation. Advances in techniques for imaging the developing brain have provided exciting opportunities for studying the mechanisms involved in the development of social cognition abilities. What remains to be initiated are programs of research to produce the first empirical studies. The overarching aim of this grant is to use fMRl to identify and characterize the neural basis of development in aspects of social cognition. We will recruit neurologically normal children and adolescents (5-14 years of age). ln this two-year longitudinal study, each child will be studied once per year. This design will provide the start of much needed longitudinal data regarding the normal development of the social brain in childhood. Our studies will focus on the development of brain mechanisms for: (1) the perception of other people's actions and intentions and (2) the formation of representations of the self and the relationship between self and others.